1. Field of the Invention
The present invention relates to an automatic tool changing assembly, and more particularly to an automatic tool changing assembly for a machine tool that can be used easily and accurately.
2. Description of Related Art
With reference to FIG. 10, a conventional machine tool (90) has a base (91), a spindle (92), a nut (93), a tool (94), an air motor (95) and a control device. The base (91) has a central hole and an engaging panel (911). The engaging panel (911) is securely mounted in the central hole of the base (91). The spindle (92) protrudes through the central hole of the base (91) and has an upper end and a lower end. The nut (93) is formed on the upper end of the spindle (92) and may abut the engaging panel (911) in the central hole of the base (91). The tool (94) is detachably connected to the lower end of the spindle (92). The air motor (95) is mounted on the base (91) above the spindle (92) and has a driving axle and a jacket (951). The jacket (951) is connected to the driving axle and is selectively mounted around the nut (93). The control device is connected to the air motor (95) and has an air valve, two controlling buttons, two induction pipes (96) and an inlet pipe. The controlling buttons are used to control the air valve. One of the induction pipes (96) is connected to the air motor (95) and the other induction pipe (96) is connected to the jacket (951). The inlet pipe is connected to the air valve.
The tool (94) is selectively held by the spindle (92) by pressing one of the controlling buttons to let air flow into the air motor (95) and the jacket (951) via the induction pipes (96) to make the spindle (92) rotate and hold the tool (94). When the tool (94) needs replacing, the controlling button is pressed to let the air flow into the air motor (95), the jacket (951) and the air valve via the induction pipes (96) and the inlet pipe to force the spindle (92) to rotate in an inverse direction and separate from the tool (94).
However, the conventional machine tool has the following defects and shortcomings.
1. As the spindle (92) is rotated with the jacket (951) to loosen the tool (94) by the air motor (95), air enters the induction pipe (96) and the inlet pipe at a same time and this decreases the force of the air motor (95) to loosen the tool (94).
2. The engaging panel (911) of the base (91) that may abut the nut (93) merely provides a holding effect and prevents the jacket (951) from moving and obtaining good contact with the nut (93).
3. Although the driving axle of the air motor (95) can rotate the jacket (951) forward and reverse to loosen or fasten the tool (94), the driving axle cannot rotate stably and this will influence the operation of changing the tool (94) of the conventional machine tool (90).
The automatic tool changing assembly for a machine tool in accordance with the present invention mitigates or obviates the aforementioned problems.